problem w/ piston size

[Munkee]

so my friend was rebuilding her engine in her talon, and ordered pistons w/o checkin the engine first. She ordered 85mm Ross pistons, but later found the block had been bored to 85.5 (she's the 2nd owner). The mechanic is tellin her the pistons will be fine if u gap the rings right...and allow for expansion...im not so sure that much rooom is ok though. What do u guys think?

 

[1fast97gsx]

I think there's a reason they make oversized pistons...

 

[sweet97]

Yeah she should exchange them for the .020' overs she needs. Should check to see if the block needs to be bored even more first! mark

 

[92redman]

so my friend was rebuilding her engine in her talon, and ordered pistons w/o checkin the engine first. She ordered 85mm Ross pistons, but later found the block had been bored to 85.5 (she's the 2nd owner). The mechanic is tellin her the pistons will be fine if u gap the rings right...and allow for expansion...im not so sure that much rooom is ok though. What do u guys think?

No, that is not okay. .5mm is roughly .020". I am going to be running .006" clearance on my Ross pistons. The correct clearance for a mild boost application without nitrous is about .0045". You would have a clearance of about .024" since Ross already includes the clearance in their pistons.

 

[jott5555]

slap the mecahnic and order the correct pistions..

 

[half-cocked]

After you slap the mechanic, go find a new one. What else is he going to do/ tell you to do that is idiotic like that.

EDIT: I have Ross pistons and have talked to their people alot with question and they live by their rep. As long as they are off the shelf ross pistons adn they arent damaged they will take them back. Well that is if you ordered them from Ross.

 

[blue1]

you will have that much piston slap your knock sensor will give you no timing at idle even